Telling your players - hey, up to you. Some people really dislike analytical or principle-based statements regarding stuff they do. If it's not about how it feels when they do it, then they don't wanna know. Based on your third session, I suggest simply continuing to play and exercise your own understanding and skills.

If you simply must present any specific thing to them from this conversation, I suggest pointing out that content authority lies with you, and that they can rely on you to provide it when desired. So (a) they can describe stuff and (b) they can cue you to provide some content, or that they'd like a conflict in order to get some. This is a pretty useful and jargon-free way to present it, I think.

To put it as simply as possible, stick with "prep content" or "back story," and distinguish it from "description," and then play it from there. You'll probably find that that's a relief to them, because some people's freeze-up with narrational mechanics lies with their misconception that they are supposed to be adding content.

Regarding The Pool and the Jasmine game, I'll tell you my viewpoint based on many discussions with James, although not based on the text one way or the other.

a) I do not think The Pool was written to provide players with content authority. This should be left to the GM and prep. The Pool is not a mere improv freeform activity in which we trade around "telling a story."

b) It obviously provides narrational authority, per use of Monologues of Victory. Each Monologue carries a strong optional possibility, to generate one-scene plot authority. I have noted many times that players vary greatly in their desire to exercise this option; many are stunned by the narrational authority alone and do not need to be pushed for more. Many stick with narrational authority and choose their instances to "upgrade" it to plot authority very carefully.

Example (winning roll to charm someone): "He smiles and takes my arm, and we whirl off together into the dance." (narrational)

c) Situation authority is fuzzy, and in my view, is probably best left to the GM.

Regarding the Jasmine game, I didn't provide much instruction, but rather clarifications during play itself as people squinted or looked puzzled when they thought about using the Monologues. The opportunity to explain was easy to isolate, because a successful roll presents the mechanical choice of taking a die or narrating, so a built-in pause exists.

The fellow playing the successful suitor was the most experienced with The Pool, so he simply kept adding dice to his pool, to the maximum (from memory ... nine dice, I think), and then only used the Monologue when he really wanted to, i.e., winning Jasmine's heart.